Field of the Invention
The present disclosure relates to an electrophotographic image forming apparatus, such as a multifunction apparatus or a copying machine, which includes a reading unit.
Description of the Related Art
In a typical electrophotographic image forming apparatus, after a rotating photoconductor is uniformly charged with a charger, the photoconductor is exposed to light in accordance with image data to form an electrostatic latent image. The image forming apparatus develops the electrostatic latent image with toner and transfers the developed toner on a sheet for fixing. A configuration is used in which a desired image is printed through such an image forming process.
In the electrophotographic method, density unevenness may occur in a toner image formed on a sheet in a rotation axis direction of the photoconductor. This unevenness is caused by variation in the intensity of light used to form an electrostatic latent image on the photoconductor or variation in the sensitivity of the photoconductor to light.
In order to suppress the density unevenness in the rotation axis direction of the photoconductor, Japanese Patent Laid-Open No. 2011-133771 proposes the following configuration. Specifically, in the configuration proposed in Japanese Patent Laid-Open No. 2011-133771, multiple test patterns are printed on a sheet in the rotation axis direction of the photoconductor. The sheet on which the test patters are printed is fed again and the multiple test patterns are read with a density sensor provided on a sheet conveyance path. The laser intensity is adjusted at each position in a main scanning direction on the basis of the density that is read.
The sheet that has reached a transfer unit may be shifted from a desired position in the rotation axis direction of the photoconductor. In other words, desired positional relationship may not be established between the position of the sheet that has reached the transfer unit and the position of the toner image in the rotation axis direction of the photoconductor. The image forming apparatus generally corrects the positional relationship between the sheet and the toner image by adjusting the position of the electrostatic latent image to be formed on the photoconductor. However, in a case where the test images for correcting the density unevenness are printed, as in the disclosure described in Japanese Patent Laid-Open No. 2011-133771, the adjustment of the position where the electrostatic latent image is formed may reduce the correction accuracy of the density unevenness. This is because the adjustment of the position where the electrostatic latent image is formed shifts the position of the toner image in the rotation axis direction of the photoconductor from the position on the photoconductor to be corrected to.